1. Technical Field
The present disclosure relates to a solar cell system.
2. Description of Related Art
An operating principle of a solar cell is photoelectric effect of a semiconducting material. The solar cells can be roughly classified into silicon-based solar cells, gallium arsenide solar cells, and organic thin film solar cells.
A silicon-based solar cell commonly includes a rear electrode, a P-type silicon layer, an N-type silicon layer, and a front electrode. The P-type silicon layer can be made of polycrystalline silicon or monocrystalline silicon and has a first surface and a flat second surface opposite to the first surface. The rear electrode is disposed on and in ohmic contact with the first surface of the P-type silicon layer. The N-type silicon layer is formed on the second surface of the P-type silicon layer and serves as a photoelectric conversion element. The N-type silicon layer has a flat surface. The front electrode is disposed on the flat surface of the N-type silicon layer. The P-type silicon layer and the N-type silicon layer cooperatively form a P-N junction near an interface of the P-type silicon layer and the N-type silicon layer. In use, light directly irradiates the front electrode, and reaches the P-N junction through the front electrode and the N-type silicon layer. Consequently, a plurality of electron-hole pairs (carriers) can be generated in the P-N junction due to photon excitation. Electrons and holes in the electron-hole pairs can be separated from each other and separately move toward the rear electrode and the front electrode under an electrostatic potential. If a load is connected between the front electrode and the rear electrode, a current can flow through the load.
However, a light absorbing efficiency of the P-N junction of the above solar cell is low, because partial photons in the incident light are absorbed by the front electrode and the N-type silicon layer. Thus, carriers generated by exciting of photons in the P-N junction are relatively few, and a photoelectric conversion efficiency of the solar cell is relatively low.
What is needed, therefore, is to provide a solar cell having high photoelectric conversion efficiency, and a solar cell system using the same.